1. Field of the Invention
The present invention relates to a polarizing unit to achieve illuminating light made up of, for example, linearly polarized light, a polarizing illumination device using a same polarizing/unit and a projection display device using a same polarizing/illumination.
The present application claims priorities of Japanese Patent Application Nos. 2001-337827 filed on Nov. 2, 2001 and 2002-207553 filed on Jul. 16, 2002, which are hereby incorporated by reference.
2. Description of the Related Art
In recent years, a step toward miniaturization and high definition proceeds and improvements of an optical system making up a projection display device is made. In particular, as a method for improving brightness of a projected image and uniformity of illumination of a screen both being a requirement for performing functions of a display device, an optical system configured by combining an integrated optical system made up of fly""s eye lens with a polarized light converting optical system made up of a polarized light beam splitter array has become commercially practical and therefore an optical system using three pieces of liquid crystal display devices being currently on the market has the configuration described above.
In the optical system having the above configuration, by dividing light fed from a light source into a plurality of pieces of partial light using an integrated optical system made up of two pieces of fly""s eye lens to form a plurality of light source images and by comparing the light source image to a secondary light source, and by superimposing light on the liquid crystal display devices, illuminating light having same distributions of intensity of light can be effectively obtained.
Moreover, by using the polarized light converting optical system made up of polarized beam splitter arrays and integrated optical systems in combination, illuminating light is superimposed on a liquid crystal panel after having divided light into a plurality of pieces of partial light and having converted polarized light, that is, after same polarization directions have been provided and, therefore, efficiency of using a light source is comparatively high.
However, in such the projection liquid crystal display device having configurations as described above, in ordinary cases, since sizes of the fly""s eye lens and the polarized beam splitter array become larger than those of an image display portion of the liquid crystal display device serving as a surface to be illuminated, a diverging angle of incident light into the liquid crystal display device becomes large. When the diverging angle of incident light becomes large and, therefore, when parallelism of incident light into the liquid crystal panel is reduced, light cannot be applied effectively to the liquid crystal panel and, as a result, efficiency of using light is lowered. Moreover, in order to improve an aperture ratio of the liquid crystal panel, the liquid crystal display device having a microlens array is also commercially available, however, it is known that, in the projection liquid crystal display device, unless light having high parallelism is incident on the microlens, efficiency of using light transmitting through a pixel opening portion is reduced.
Conventional optical systems aimed at reducing a diverging angle of light being incident on a liquid crystal display device are disclosed in Japanese Patent Application Laid-open Nos. 2000-131647 and 2001-206464 in which an illumination unifying unit using a columnar integrated device (mainly, rod integrator) and a polarized light converting unit are combined. In the conventional optical systems, as a polarized light separating unit, an optical system in which a plurality of polarized light beam splitter arrays each having a polarized light separating film formed on a junction face between a rectangular prism and a wedge-type prism or a plurality of polarized light beam splitters are arranged in an array form.
However, since a device to obtain uniformity of illumination and a device to convert polarized light are independently arranged in both the conventional optical systems described above, physical space to house them is required. Since a polarized light beam splitter made of glass used, in particular, in the conventional optical system provided as the disclosed former example becomes relatively large, the conventional optical system is not suitable in realizing a small-sized projection display device. Moreover, the conventional optical system has a disadvantage in a point of costs. Since two rod integrators, one to be used for p-polarized light and another to be used for s-polarized light, each being separated by polarization, are required, the conventional optical system is not suitable in a point of making it lightweight and costs low. In the optical system provided in the disclosed latter example, since a necessary number of the rod integrators is one and polarized light converting process is performed using the polarized light beam splitter array, it is advantageous in point of weight and costs when compared with the optical system provided in the disclosed former example. However, since the optical device to be used for uniformity of illumination and the optical device to be used for polarized light conversion are independently placed, space for arrangement has to be secured and it lacks in a point of making the illuminating device compact.
In view of the above, it is a first object of the present invention to provide a polarizing unit which is capable of making compact an optical system made up of a columnar integrated device (mainly, rod integrator) and a polarized light converting optical system and of reducing a diverging angle of light being incident on a comparatively smaller liquid crystal panel. It is a second object of the present invention to provide a new type polarizing illumination device which is made small and lightweight when compared with a conventional polarizing illumination device and is capable of reducing a diverging angle of light being incident on a comparatively small liquid crystal panel by using the above polarizing unit. It is a third object of the present invention to achieve miniaturization of a single plate display device of a time-sharing type made up of an LCOS (Liquid Crystal On Silicon) and a projection display device made up of a microlens, by utilizing the above new type polarizing illumination device.
According to a first aspect of the present invention, there is provided a polarizing unit for receiving light fed from a light source and for emitting polarized-illuminating light to an subject to be illuminated, the polarizing unit comprising:
a polarized light converter (polarized light converting means) used to obtain a specified type of polarized light and, when polarized light is incident from a side of the subject to be illuminated, to convert a phase difference between two light components whose polarized directions orthogonal to each other and to emit the polarized light to a side of the subject to be illuminated;
a light guiding member (light guiding means) having a light incident end face formed on a side of the light source and a light outgoing end face formed on a side of the subject to be illuminated and used to have incident light travel in a straight line or have internal reflection occur to guide the light;
a polarized light separator (polarized light separating means) to separate a specified type of polarized light from an other specified type of polarized light and to transmit the separated polarized light; and
wherein the polarized light converter and the light guiding member are placed on a side of the light source in the polarized light separator.
With the above configuration, the polarized light converter, light guiding member, and polarized light separator can be formed in an integrated manner. As a result, the configuration contributes to miniaturization of the polarizing unit.
In the foregoing, a preferable mode is one wherein the polarized light converter has a reflector (reflecting means) with an opening which receives light emitted from the light source through an opening portion and reflects light being incident from a side of the subject to be illuminated and a phase delaying device (phase delaying means) being placed on a side of the subject to be illuminated of the reflector with the opening and wherein the reflector with the opening, the phase delaying device, the light guiding member are placed on a side of the light source of the polarized light separator.
With the above configuration, the reflector with the opening, phase delaying device, light guiding member, and polarized light separator can be arranged in an integrated manner. As a result, the configuration contributes to miniaturization of the polarizing unit.
Also, a preferable mode is one wherein the phase delaying device is placed between the reflector with the opening and the light guiding member.
With the above configuration, by configuring the reflector with the opening and the phase delaying device so as to come into contact with the light incident end face of the light guiding member, the reflector with the opening, phase delaying device, and the light incident end face of the light guiding member can be formed in an almost integrated manner and therefore the polarizing unit can be made compact.
Also, a preferable mode is one wherein the phase delaying device is placed between the light guiding member and the polarized light separator.
With the above configuration, by configuring the reflector with the opening so as to come into contact with the light incident end face of the light guiding member and by configuring the phase delaying device so as to come into contact with the light outgoing end face, the reflector with the opening, phase delaying device, and light guiding member can be formed in an almost integrated manner and therefore the polarizing unit can be made compact.
Also, a preferable mode is one wherein the light guiding member is made up of a solid or hollow columnar integrated device.
With the above configuration, the light being incident on the light incident end face is reflected totally to achieve uniformity of luminance and is guided to the light outgoing end face. Since internal reflection is used, superimposing illumination is performed on the light outgoing end face using luminous flux having less light convergence and therefore illumination having comparatively high parallelism can be made on a surface to be illuminated.
Also, a preferable mode is one wherein the reflector with the opening has the opening portion without a reflecting face being placed in its almost central portion and the opening portion allows light to be transmitted and other portions except the opening portion reflect light.
With the above configuration, randomly polarized light having transmitted through the opening portion of the reflector with the opening is incident on the polarized light separator through the phase delaying device and the light guiding member and another light component having been reflected off the polarized light separator travels backward to the light source and, after having passed through the light guiding member and the phase delaying device, is reflected off, for example, the reflector with the opening and is incident on the polarized light separator through the light guiding member and therefore light fed from the light source can be effectively used.
Also, a preferable mode is one wherein the phase delaying device is a quarter-wave plate.
With the above configuration, since the quarter-wave plate is used as the phase delaying device, another light component having been reflected off the polarized light separator travels backward to the light source and, after having transmitted through the light guiding member and the phase delaying device, is reflected off, for example, the reflector with the opening and is again incident on the polarized light separator through the phase delaying device and therefore is converted into linearly polarized light orthogonal to the previous polarized light direction which can transmit through the polarized light separator. As a result, light fed from the light source can be effectively used.
Also, a preferable mode is one wherein the columnar integrated device is made of glass or plastic and wherein the light incident end face and the light outgoing end face are of a rectangular square pole shape and wherein the columnar integrated device totally reflects light being incident on the light incident end face by a surrounding side face and to guide the light toward the light outgoing end face.
With the above configuration, the columnar integrated device made up of glass or plastic whose light incident end face and light outgoing end face are of a rectangular square pole shape totally reflects light being incident on the light incident end face by a surrounding side face to achieve uniformity of luminance and guides light to the light outgoing end face. Since internal reflection is used, superimposed illumination is made on the light outgoing end face using luminous flux having less light divergence, thus enabling illumination having a comparatively high parallelism on a surface to be illuminated.
Also, a preferable mode is one wherein the columnar integrated device is made of glass or plastic and wherein the light incident end face and the light outgoing end face are of a circular cylindrical shape and wherein the columnar integrated device totally reflects light being incident on the light incident end face by a surrounding side face and to guide the light toward the light outgoing end face.
With the above configuration, by using a circularly cylindrical integrated device as a light guiding member, the polarizing unit can be fabricated at lower costs compared with a case where the square pole shaped columnar integrated device is employed.
Also, a preferable mode is one wherein, on a side of the light outgoing end face of the columnar integrated device is placed a rectangular opening portion and the reflector with the opening using a surface on a side of the light source as a reflecting surface.
With the above configuration, since the reflector having the rectangular opening portion in a vicinity of the light outgoing end face of the columnar integrated device, for example, the liquid panel serving as an subject to be illuminated can be illuminated in a manner that a shape of an area being illuminated is rectangular and reduction of efficiency of illumination and of using the light source can be avoided.
Also, a preferable mode is one wherein a size of the polarized light separator is set to be larger than that of the rectangular opening portion.
With the above configuration, since a size of the polarized light separator is set to be larger than that of the rectangular opening portion of the reflector with the opening, light reaching the subject to be illuminated of the polarized light separator is all desired linearly polarized light that can be used to illuminate the subject to be illuminated.
Also, a preferable mode is one wherein the polarized light separator transmits only one component out of two linearly polarized components orthogonal to each other contained in randomly polarized light being incident and reflects another component out of the two linearly polarized components.
With the above configuration, it is made possible to apply linearly polarized light to the subject to be illuminated.
Also, a preferable mode is one wherein the reflector with the opening and the phase delaying device are configured so as to come into contact with the light incident end face of the light guiding member.
With the above configuration, by forming the reflector with the opening, phase delaying device, and light guiding member in an integrated manner, it is possible to make the polarizing unit be small-sized and lightweight.
Also, a preferable mode is one wherein the reflector with an opening is configured so as to come into contact with the light guiding member and the phase delaying device are configured so as to come into contact with the light outgoing end face.
With the above configuration, by forming the reflector with the opening, phase delaying device, and light guiding member in an integrated manner, it is made possible to make the polarizing unit be small-sized and lightweight.
Also, a preferable mode is one wherein the reflector with the opening is formed by vacuum evaporation on the light incident end face of the light guiding member.
With the above configuration, since the reflector with the opening is formed by vacuum evaporation on the light incident end face of the light guiding member, it is made possible to make the polarizing unit be compact.
According to a second aspect of the present invention, there is provided a polarizing illumination device for achieving uniformity of illumination and polarized light conversion by using the polarizing unit described above, including:
a light source;
a light condensing device to condense light fed from the light source;
the polarizing unit; and
a condenser lens to gather light having passed through the polarized light separator on the subject to be illuminated.
With the above configuration, randomly polarized light having been gathered by the light condensing device and having transmitted through the opening portion of the reflecting device with the opening enters the polarized light separator through the phase delaying device and the light guiding member. One light component out of two linearly polarized light components whose polarizing axes orthogonal to each other transmits the polarized light separator and is used to illuminate the subject to be illuminated through the condenser lens. Another light component having been reflected by the polarized light separator travels backward to the light source and reaches the reflector with the opening through the light guiding member and the phase delaying device. In one case, the light having reached the reflector is reflected off the reflector with the opening. In another case, the light having reached the reflector transmits through the reflector with an opening and is again gathered by the light condensing device and then transmits through the reflector with the opening. In any case, the above light transmits through the phase delaying device twice before the light again reaches the polarized light separator through the light guiding member. Since the light has been converted into linearly polarized light intersecting the previous polarizing direction at right angles, the light can transmit through the polarized light separator. Therefore, the light can be used as illuminating light. Since an image showing uniform illuminating information on the light outgoing end face of the light guiding member is formed by the condenser lens, uniform illumination is made possible. Thus, randomly polarized light fed from the light source is converted into linearly polarized light with high efficiency and is illuminated in a uniform manner.
According to a third aspect of the present invention, there is provided a projection display device including:
the polarizing illumination device stated in claim 16,
a color separator to separate light emitted from the polarizing illumination device into a plurality of primary colors of light;
a light valve serving as the subject to be illuminated to electrooptically modulate light fed from the color separator; and
a projection lens to project light of picture image modulated by the light valve in an enlarged manner. With the above configuration, a projected image being excellent in uniformity and having comparatively high parallelism can be obtained. Moreover, since the polarizing illumination unit becomes very compact, the projection display panel becomes small-sized and can be suitably used, as a display device, for a time-sharing single plate projection liquid crystal display using an LCOS or for a projection liquid crystal display device using a microlens. As the color separating device, for example, a color filter can be employed. As the light valve, for example, the liquid crystal panel can be employed.